Low energy use was a particular priority for the Triskelion, a 1,300-square-foot moveable pavilion commissioned by the nonprofit arts organization FOR-SITE. Designed by Ogrydziak/Prillinger Architects, San Francisco, the building consists of three shipping containers arranged at 120-degree angles to define a central skylit atrium. Since May 2010 it has been installed at the Presidio, where it was part of the yearlong Presidio Habitats'an exhibition of artist-created animal habitats distributed around one corner of the national park. The pavilion served as a space for the display of sketches and models.

Because Presidio officials required that the building be easily demountable and leave no trace of its existence once removed, the Triskelion could not tie into nearby utilities. It needed to be completely 'untethered' from the site, says architect Luke Ogrydziak.

To meet the requirement, the project team devised an off-the-grid lighting scheme largely dependent on daylight penetrating the central skylight, windows at the ends of each container, and side openings. But for those times when daylight is insufficient, the power generated by a rooftop 4,440-W photovoltaic array illuminates photo-sensor-controlled T5 lamps inserted within fabric-covered coves. The light evenly washes the walls, creating an effect different from that found in most gallery settings, where individual pieces of art are typically highlighted against a dark background, explains George Loisos, principal of Bay Area'based Loisos + Ubbelohde, the project's lighting and daylighting consultant. The more usual approach would have required track lights, but the containers had insufficient headroom, he says. The chosen strategy also offered the advantage of keeping the ceiling clear of fixtures, making the skylight opening seem like an abstract cut in the drywall plane, points out Ogrydziak.

One challenge was positioning the dimming sensors, since daylight enters the building from multiple directions. To identify the best spots, Loisos's team moved the sensors within a virtual model and then simulated the response of the electric lights.

The Triskelion will remain at the Presidio through October and will host workshops associated with the 75th anniversary of the Golden Gate Bridge. FOR-SITE is considering options for the pavilion once the workshops end, including erecting it elsewhere in the city for use as its own offices.